it has made specialization possible in other directions: specialization of fibers [i.e, change from tracheids to libriform
grandis is a hardwood tree species with a diverse range of anatomical features that can be characterized as vessel frequency, solitary vessel percentage, vessel diameter, vessel member length, fiber length and diameter, libriform
fiber length, ray frequency, and ray height (Chang-ming and Xin-ying 1994).
Vessels and a parenchyma cells are embedded in a tissue consisting of thin-walled libriform
, of medium length, fine diameter and thick walls.
Implicit in the concepts of Bailey (1944) and the tabular data on bordered pits by Metcalfe & Chalk (1950, xlv) is the idea that the tracheid is the primitive (plesiomorphic) type of imperforate tracheary element in angiosperms, and that it has evolved, in'evcrsibly, into fiber-tracheids in various clades, followed by libriform
High degree--rupturing wood cell pore membranes, resin boiling and replacement, destroying tyloses (in hardwood species), rupturing ray cells, rupturing main cell (traheids, libriform
, parenchyma) walls and walls of vessels, and formation of cavities being primarily in radial--longitudinal planes.
The wood presents extremely short vessel elements, with alternate areolate punctuations, and simple perforated plates, vasicentric axial parenchima, confluent stripes, uniseriated rays, extremely short, fine and very short libriform
These cells have been reported to be libriform
fibers, but SEM study reveals small borders (Fig.
For example, the diameter of the largest vessel elements of Populus tremuloides, one of the typical wood species used in OSB production, is 50 [micro]m to 100 [micro]m; and its libriform
fibers are 20 [micro]m to 30 [micro]m (Panshin and deZeeuw 1980).
These species have diffuse porosity, alternate vessel pits, simple perforation plates, numerous and small rays; libriform
fibres are common, as well as ergastic material in gum forms, calcium carbonate and silica crystals.
For example, rather than representing "noise" and "aberrations", it seems just as plausible that selection should favor very high variation in features such as libriform
fiber length; high variability in length could be favored by selection in that it would diminish the occurrence of fracture planes that would result if cells were aligned, while still resulting in mechanical and hydraulic characteristics that meet the needs of the stem given its size.